1. Technical Field
This disclosure generally relates to prostheses and, in particular, adjustable prostheses and/or ventilated prostheses.
2. Description of the Related Art
Amputees often wear prostheses that are uncomfortable, especially if worn for an extended period of time. A prosthetic interface is often the greatest source of discomfort and may also cause a wide range of problems. Poorly fitting sockets of prostheses often cause blisters, ulcers, skin breakdown, infections, and other unwanted skin conditions. Conventional prosthetic liners typically trap moisture (e.g., perspiration) next to the user's skin, contributing to these problems.
A residual limb often changes shape and volume over short periods and long periods of time. These changes can cause problems with the fit of the prosthesis, leading to a wide range of different types of unwanted conditions (e.g., blistering, ulcers, skin breakdown, abrasions, infections, and the like) requiring treatment by a physician, disuse of the prosthesis, and the like.
Conventional prostheses often have a rigid socket lined with a soft liner. The soft liner provides cushioning to enhance comfort. The rigid socket transfers loads to the user's skeleton and provides stability during a stance phase of a gait and suspends the prosthesis during a swing phase of the gait. Unlike the fatty pad under the heel of an intact foot, soft tissue of a residual limb is not well suited to bear loads.
Some sockets have bladder systems that can be inflated to adjust comfort and fit. These bladder systems are often located between a rigid outer shell of the socket and the residual limb. It is often difficult to maintain suitable pressures in the bladder systems because of the repeated applied loads during use, as well as the compliance of the materials forming the bladders. Thus, bladder systems are not suitable for long term use.
To keep a prosthetic's socket fitted to a user, a vacuum can be applied between the user's skin and the socket. Air is drawn from a cavity of the socket using a negative pressure. Unfortunately, negative socket pressures often cause contact dermatitis, verrucous hyperplasia, and significant discomfort. There is a limited number of amputees with chronic residual limb sores for whom the drawbacks of a poorly-fitting socket are outweighed by the benefits of negative pressure therapy to heal the wounds.
If the prosthesis has poor thermal conductivity properties, the prosthesis can function as a heat capacitor that stores thermal energy. This can lead to an elevated residual limb temperature that promotes perspiration and blistering. Unfortunately, these types of prostheses are not suitable for extended use, especially if worn in a relatively hot environment or if worn to perform vigorous exercises.